Lipopeptides are cyclohexapeptides, which can be obtained by fermentation, and have a systemic antifungal activity entailing inhibition by them of (1,3)-β-D-glucan synthase, a key enzyme in fungal cell wall biosynthesis. Lipopeptides also have antibacterial activity (Exp. Opin. Invest Drugs 2000, 9, 1797-1813). It is known that lipopeptides have unfavorable physicochemical properties, such as slight solubility in water or instability in alkaline solution. In addition, natural lipopeptides show severe side effects such as damage to the venous endothelium, destruction and inflammation of tissues or local toxic effects at the site of administration.
There is thus a need to synthesize novel lipopeptides having improved pharmacokinetic and chemotherapeutic properties as well as lower toxicity. Such semisynthetic modifications generally consist of introducing acidic or basic groups into the molecular structure and of replacing the natural aliphatic side chain acid by aromatic acyl components. Modification of the fatty acid side chain (N-acyl side chain) in particular has central importance in partial syntheses of lipopeptides. This generally takes place by eliminating the N-acyl side chain of lipopeptides by enzymatic means using a natural, cell-associated or recombinant deacylase of broad substrate specificity, and reacylating the resulting peptide ring, called the nucleus, with a modified activated acid (for example EP 1 189 932; EP 1 189 933).
European patent application EP 0 460 882 describes the deacylation of the lipidic acyl position of lipopeptides using purified echinocandin B decyclase. The enzyme is produced by fermentation of Actinoplanes utahensis (NRRL12052), it being in cell-associated form after the fermentation, and initially being detached from the cells by salt treatment before the dissolved enzyme obtained in this way is purified in an eight-stage method.
Enzymatic elimination of side chains from lipopeptides generally takes place by mixing the purified lipopeptide with a culture or a culture supernatant of a microorganism which produces a deacylase of broad substrate specificity. This may be a natural Actinoplanes utahensis strain (e.g. NRRL 12052; WO00/75177 and WO00/75178) or a recombinant deacylase producer such as, for example, a recombinantly modified Streptomyces lividans strain. A further alternative method is to add a purified deacylase to a solution or suspension of the purified lipopeptide. After the side chain has been eliminated, the reaction supernatant is freed of insoluble constituents, and the water-soluble nucleus present in the filtrate is purified. This procedure using purified or partially purified substrates is time-consuming and inapplicable on the industrial scale.